a) Field of the Invention
This invention relates to apparatus for detecting a leak in a pipe, as well as a method of determining the location of such a leak. The invention finds a particular application to the detection of the location of a leak in an underground pipe such as a water pipe, though it is to be understood that the invention is not limited to that particular use.
b) Description of the Prior Art
Fresh drinking-quality water as piped to residential and business premises is a valuable commodity and recently much emphasis has been placed on the elimination of leaks in the pipe network taking the water from a water-works to each premises requiring water. It is relatively easy to determine whether there is a leak in a given length of pipe, but it is very much more difficult to determine the precise location of that leak. For example, a pipe may be closed off at two points where access can be gained to the pipe, the water in the pipe then being pressurised. By disconnecting the source of pressure and then monitoring the pressure in the pipe over a pre-set period of time, it can be determined whether there is a leak of greater than an acceptable amount, allowing for minor leakage with the test equipment.
The difficulty is establishing where the leak is, especially if the two access points are spaced apart by a considerable distance. The usual solution is to dig test-holes at spaced intervals along the length of the pipe and to monitor the water content in the ground, around the pipe. In this way, it is possible eventually to locate the region of the leak, permitting a relatively large excavation to be performed in order to effect a repair. If however the ground through which the pipe extends is relatively wet, it may not be possible to establish the location of the leak other than by much more extensive excavations.
It is a principal object of the present invention to provide apparatus for detecting a leak in a pipe, which apparatus is both simple to use and effective in determining the presence of a leak. It is a further object of a preferred form of the apparatus to facilitate the location of a leak in a pipe, once the presence of a leak has been determined.
Yet another object is to provide a method for determining the location of a leak in an underground pipe, in a simple and effective manner.
According to one aspect of the present invention, there is provided apparatus for detecting a leak in a pipe, which apparatus comprises a closure member for sealing an opening in the pipe, the closure member having an aperture therethrough, and a flexible fluid supply hose having a free end and slidably extending in a sealable manner through said aperture in the closure member. An inflatable seal member is disposed at or adjacent the free end of the hose which seal member is inflatable by fluid (such as air) supplied under pressure to the hose, there being means to supply that fluid under pressure to the interior of the pipe after the hose has been passed into the pipe through the aperture in the closure member and the seal member has been inflated. Pressure-sensing apparatus is arranged to sense the fluid pressure within the pipe following the supply of fluid under pressure to the pipe whereby a subsequent drop in pressure may be determined.
It will be appreciated that use of the apparatus of this invention requires access to a pipe at only one point. A length of the pipe from the access point may be isolated and then subjected to a pressure test. By repeating the testing process but isolating different lengths of pipe from the access point, it should be possible to determine the location of the leak (if there be one) by finding two adjacent points at one of which pressure is substantially maintained but at the other of which pressure falls away, over time.
According to a second aspect of this invention, there is provided a method of determining the location of a leak in a pipe, which method comprises fitting a closure member in a sealing manner to an opening in the pipe, the closure member having an aperture therein through which extends a flexible fluid supply hose in a slidable and sealable manner and the hose having an inflatable seal member at or adjacent its free end for inflation by fluid supplied under pressure to the hose. The hose is slid through the aperture until a known length of hose has entered the pipe, whereafter the seal member is inflated to effect a seal to the interior wall of the pipe, and then fluid under pressure is supplied to the interior of the pipe. The pressure in the pipe is sensed and monitored for a fall in that pressure in excess of a pre-set amount, over a pre-set period.
According to a further and closely related aspect of this invention, there is provided a method of determining the location of a leak in a pipe, which method comprises fitting a closure member in a sealing manner to an opening in the pipe, the closure member having an aperture therein through which extends a flexible fluid supply hose in a slidable and sealable manner and the hose having an inflatable seal member at or adjacent its free end for inflation by fluid supplied under pressure to the hose and further having, at or adjacent its free end, a device selected from the group consisting of an active transponder, a passive transponder and an electromagnetic transmitter sonde. The hose is slid through the aperture while monitoring from the surface the position of the free end of the hose by means of an electromagnetic location determining device in communication with said device at or adjacent the free end of the hose. Thereafter the seal member is inflated to effect a seal to the interior wall of the pipe, and then fluid under pressure is supplied to the interior of the pipe. The pressure in the pipe is sensed and monitored for a fall in that pressure in excess of a pre-set amount, over a pre-set period.
With either of the above methods, the location of a leak is determined by repeatedly performing the steps of inflating the seal member, supplying fluid under pressure to the pipe, sensing the pressure therein and then deflating the seal member, the position of the seal member in the pipe being progressively moved along the pipe between each inflation thereof, until a significant change in the rate of fall in the sensed pressure over the pre-set time is noted.